class_docstr: Save model at the beginning of training and after every epoch.
  
  Similar to tf.keras.callbacks.ModelCheckpoint, but this allows us to specify
  a custom save fn to call, such as the HuggingFace model.save() which writes
  .h5 files and config information.
class_docstr_tok: ["Save","model","at","the","beginning","of","training","and","after","every","epoch",".","Similar","to","tf.keras.callbacks.ModelCheckpoint",",","but","this","allows","us","to","specify","a","custom","save","fn","to","call",",","such","as","the","HuggingFace","model.save","(",")","which","writes",".h5","files","and","config","information","."]
code: def on_train_begin(self, logs=None):
      self.on_epoch_end(-1, logs=logs)
  
file_path: lit/lit_nlp/examples/tools/glue_trainer.py
imports: from collections.abc import Sequence
  import os
  from absl import app
  from absl import flags
  from absl import logging
  from lit_nlp.examples.datasets import classification
  from lit_nlp.examples.datasets import glue
  from lit_nlp.examples.models import glue_models
  from lit_nlp.lib import serialize
  import tensorflow
label_desc: Use image node_id 2 for calling the EpochSaverCallback obj's underlying member method code with example usage: obj.on_train_begin(logs) without return types